Color filters may be used in a variety of applications such as, for example, liquid crystal displays (LCDs). These color filters can be prepared using various methods of thermal mass transfer imaging using a laser beam to irradiate a donor element optionally containing a light-to-heat conversion layer, thereby effectuating a transfer of the appropriate layer onto a substrate (e.g. U.S. Pat. No. 6,242,140 Kwon et al., U.S. Pat. No. 6,682,862 Chang, et al., all incorporated herein by reference).
Typical methods of thermal mass transfer imaging are imperfect, in that, when the transfer layer is transferred from the donor element to the receiver element, a portion of the transfer layer may fail to be transferred and remains as a part of the donor element, or in that a portion of the light-to-heat conversion (LTHC) layer transfers with the transfer layer, contaminating the imaged transfer layer.
Interlayers are a proposed solution. A optional non-transferable interlayer adjacent to the optional LTHC layer is disclosed in U.S. Pat. No. 5,998,085 of Isberg, et al. Examples of interlayers are described in U.S. Pat. No. 5,725,989 incorporated herein by reference. The incorporation of an interlayer interposed between a light-to-heat conversion layer and the emissive material-containing transferable layer reduces the level of contamination of the resulting transferred image from the light-to-heat conversion layer and decreases the amount of distortion resultant in the transferred image. The interlayer may be either an organic or inorganic material. To minimize damage and contamination of the resultant transferred emissive-containing image, the interlayer preferably is a continuous coating which has a high thermal resistance and remains substantially intact and in contact with the LTHC layer during the imaging process. Suitable organic materials include both thermoset (crosslinked) and thermoplastic materials.
U.S. Pat. No. 6,461,793 Chang et al. to 3M Innovative Properties Company (the '793 patent) relates to a thermal transfer element comprising a substrate having deposited thereon (a) a light-to-heat conversion layer, (b) an interlayer, and (c) a thermal transfer layer. The thermal transfer layer may additionally comprise crosslinkable materials.
The '793 patent also provides a method for generating an image on a receptor using the above described thermal transfer element. An image is transferred onto a receptor by (a) placing in intimate contact a receptor and the thermal transfer element described above, (b) exposing the thermal transfer element in an imagewise pattern with a radiation source, and (c) transferring the thermal transfer layer corresponding to the imagewise pattern to the receptor, with insignificant or no transfer of the light-to-heat conversion layer. When the thermal transfer layer contains crosslinkable materials, an additional curing step may be performed where the transferred image is subsequently crosslinked by exposure to heat or radiation, or treatment with chemical curatives.
U.S. Pat. No. 6,228,543 Mizuno et al. to 3M Innovative Properties Company, relates to thermal transfer elements and methods of transferring layers from the thermal transfer elements, as well as the articles formed by these methods. An optional interlayer can be used in the thermal transfer element to minimize damage and contamination of the transferred portion of the transfer unit and/or reduce distortion in the transferred portion of the transfer unit. The interlayer may also influence the adhesion of the transfer layer to the rest of the thermal transfer element. The interlayer typically remains in contact with the LTHC layer during the transfer process and is not substantially transferred with the transfer unit. Suitable interlayers include, for example, polymer films, metal layers (e.g., vapor deposited metal layers), inorganic layers (e.g., sol-gel deposited layers and vapor deposited layers of inorganic oxides (e.g., silica, titania, and other metal oxides)), and organic/inorganic composite layers. Organic materials suitable as interlayer materials include both thermoset and thermoplastic materials. Suitable thermoset materials include resins that may be crosslinked by heat, radiation, or chemical treatment including, but not limited to, crosslinked or crosslinkable polyacrylates, polymethacrylates, polyesters, epoxies, and polyurethanes. The thermoset materials may be coated onto the LTHC layer as, for example, thermoplastic precursors and subsequently crosslinked to form a crosslinked interlayer.
Some imaging processes result in the incomplete transfer of the entirety of the transfer layer, thereby leaving the portion of the transfer layer deposited onto the receiver element with a rough surface, e.g., a surface having a high root mean square roughness Rq value.